Polyimide resin has excellent heat resistance, an excellent electrical insulating property, excellent chemical resistance, and a mechanical property, and therefore is used for electric and electronic purposes. For example, the polyimide resin is used as materials of (i) an isolation film and a protective coating agent provided on a semiconductor device, (ii) a surface protective material and a base material resin for a flexible circuit substrate, an integrated circuit, and the like, and (iii) an interlayer insulating film and a protective film for a fine circuit. Particularly, in a case where the polyimide resin is used as a coating material for wiring lines on a substrate, the polyimide resin is used in a form of, for example: a cover lay film that is obtained by applying an adhesive agent on a shaped product such as a polyimide film; or a liquid cover coat ink made from the polyimide resin and the like.
As the polyimide resin solution used as the liquid cover coat ink, there have been proposed, for example, a polyimide resin soluble in an organic solvent and a polyimide resin composition using a thermosetting resin such as epoxy resin (see, for example, Patent Literatures 1 to 4).
Further, there has been proposed a curable imide resin composition in which a low-molecular-weight amide-imide resin having a carboxyl group and/or a low-molecular-weight imide resin having a carboxyl group, and an epoxy resin are dissolved (for example, see Patent Literature 5).
Further, there has been proposed a curable resin composition containing an epoxy resin and an imide oligomer having an acid anhydride group at its terminal, which imide oligomer is obtainable from an asymmetric aromatic or cycloaliphatic tetracarboxylic acid dianhydride and diamino polysiloxane (for example, see Patent Literature 6).